Stair climbing has become recognized as a particularly effective type of aerobic exercise and as a result, exercise machines facilitating this type of exercise are becoming increasingly popular for both home and health club use.
There have been a variety of approaches taken in designing stair climbing apparatus including the simulation of an actual stair case as illustrated in U.S. Pat. Nos. 3,497,215 and 4,687,195. Another popular approach has been to simulate he action of stair climbing by using a pair of reciprocating pedals. Examples of this approach are disclosed in U.S. Pat. Nos.: Des. 263,490, 3,316,819, 3,529,474, 3,628,791, 3,979,302, 4,496,147, 4,600,187, 4,676,501, and 4,720,093.
In U.S. Pat. No. 4,708,388, a stair climbing apparatus is disclosed where two pedals operate independently of each other and they are connected to an alternator through a speed increasing transmission that, in turn, is connected to the pedals by a pair of chains running over a pair of one way drive sprockets. A microprocessor is used to control the alternator so that a variety of exercise programs can be implemented. However, because the pedals operate independently, the range of step motion is not measured and it is not, therefore, possible to provide the user with all the desired information, i.e., step range and effort range, regarding his exercise equipment.
Along with substantial forces exerted on the two pedals and the drive chains by users as they step up and down on the pedals, there are also sudden reversals in the pedal motion and the direction of movement of the drive chain. Thus, it has been found, results in significant wear of the drive chain as its movement is reversed from one direction to another. In addition, the drive chain, itself, encounters much friction and resistance from its interaction with other components of the stair climbing apparatus such as the sprockets over which the chain is run. This abrasion caused by the other machine parts, reduces both the life of the chain and the smoothness of the simulated motion of stair climbing to the user.
Since both the expense of changing chains and the down time of the stair climbing apparatus can be a significant cost to the owner of the stair climbing apparatus, it is desirable to increase the life of the drive chain. It is also desirable to provide the user with information regarding his exercise equipment.